The Brunei customs folks gave us a hard time about turning up without any local currency.
We had to ride back 20 km (back out through Malaysian border control), then find a bank that accepted our Australian ATM cards (third one did), then find a money changer.
The only money we could get was a Brunei $100. and the customs dude was adamant that they don’t keep change, so he was all set to keep it. We declared that we were going back to Malaysia and not returning, so he got some change from his wallet.
Just supposing we’d arrived at the airport on an international flight…